1. Field of the Invention
The present invention relates to an electronic component and a method of producing the same, and more particularly to an electronic component, such as a high-frequency composite module used in the communication field, having a structure in which a surface-mount part is accommodated in a case, and a method of producing the same.
2. Description of the Related Art
One method of producing an electronic component 60 having a structure in which surface-mount parts 64 are accommodated in a shield case 65 is illustrated in FIG. 9. It is disclosed in, for example, Japanese Unexamined Patent Publication No. 10-13078.
According to this method, the electronic component 60 is producing by carrying out the following steps 1 to 6.
Step 1: As shown in FIG. 10, through holes 62 are formed in a sheet board 61 comprising a plurality of boards 51 for mounting parts thereon, and electrodes 63 for mounting shield cases 65 thereon are formed at side surfaces defining the through holes 62.
Step 2: Then, the surface-mount parts 64 are mounted onto the sheet board 61, and soldered onto land electrodes (not shown) on the sheet board 61.
Step 3: After the soldering, the through holes 62 are filled with solder pastes 67.
Step 4: After the filling, pawls (engaging portions) 66 of a plurality of the shield cases 65 are inserted into their corresponding through holes 62 filled with the solder pastes 67.
Step 5: Next, the solder in the solder pastes 67 is melted in order to solder the shield cases 65 onto the sheet board 61. As shown in FIG. 9, the pawls (engaging portions) 66 of each shield case 65 are joined and affixed to the sheet board 61 by soldering them onto the electrodes 63 (see FIG. 10) in the through holes 62.
Step 6: After affixing the pawls 66, the sheet board 61 is cut along line Axe2x80x94A with, for example, a dicing machine, whereby individual electronic components 60, one of which is shown in FIG. 9, are obtained.
Accordingly, in this conventional method, after soldering the surface-mount parts 64 onto the sheet board 61 (step 2), the shield cases 65 are mounted onto the sheet board 61 in order to insert the pawls 66 into their corresponding through holes 62 filled with the solder pastes 67 (step 4). Thereafter, the solder in the solder pastes 67 filling the through holes 62 is melted in order to solder the shield cases 65 onto the electrodes 63 in the sheet board 61 (step 5). However, in this conventional method, two soldering steps, namely, the step of soldering the surface-mount parts 64 and the step of soldering the shield cases 65 are required. This restricts productivity.
In addition, in the above-described conventional method, the step of soldering the surface-mount parts 64 is generally carried out using a reflow soldering method. After soldering the surface-mount parts 64 by the reflow soldering method, the shield cases 65 are separately soldered by the same reflow soldering method. This means that the surface-mount parts 64 are put into a reflow oven twice. When the surface-mount parts 64 are put into the reflow oven twice, the properties of the surface-mount parts 64 may change because of the high temperature in the reflow oven. This results in the problem of reduced reliability of the products.
Accordingly, in order to overcome the above-described problems, it is an object of the present invention to provide an electronic component production method that allows electronic components having a structure in which surface-mount parts are accommodated in shield cases to be efficiently produced without causing changes in the properties thereof; and to provide highly reliably electronic components that are efficiently produced by this method.
To this end, according to one aspect of the present invention, there is provided an electronic component production method in which the electronic component has a structure in which a surface-mount part is accommodated in a shield case, the method comprising the steps of:
applying solder paste to a connection land electrode, to which the surface-mount part is to be electrically and mechanically connected, and a case-fixing electrode, to which an engaging portion of the shield case for accommodating the surface-mount part is to be electrically and mechanically joined and affixed, the connection land electrode and the case-fixing electrode being disposed on a printed board onto which the surface-mount part is to be mounted;
mounting the surface-mount part and the shield case onto predetermined locations of the printed board, the shield case being mounted so as to accommodate the surface-mount part therein; and
carrying out reflow soldering in order to solder at the same time the surface-mount part onto the connection land electrode and the engaging portion of the shield case onto the case-fixing electrode by putting the printed board on which the surface-mount part and the shield case are mounted into a reflow oven and melting the solder in the solder paste.
In this case, solder paste is applied to both the connection land electrode, to which the surface-mount part is to be electrically and mechanically connected, and case-fixing electrode, to which the engaging portion of the shield case is to be electrically and mechanically joined and affixed. Next, with the paste being applied, the surface-mount part is mounted onto a predetermined location of the printed board, and the shield case is mounted onto the printed board so that the surface-mount part is accommodated in the shield case. Then, the printed board is put into the reflow oven in order to solder the surface-mount part onto the connection land electrode and the engaging portion of the shield case onto the case-fixing electrode used for affixing the case thereto. Therefore, both the surface-mount part and the shield case can be mounted onto the printed board at the same time in one soldering step. Consequently, an electronic component can be efficiently produced without causing changes in the properties thereof. Since the step of melting solder can be finished only at one time and thermal stress to the surface-mount parts can be reduced, deterioration in property due to the thermal stress applied to the surface-mount parts mounted on the printed board can be prevented and the reliability can be improved.
The shield case is prevented from dropping and shielding performance can be improved in a case where stresses from other directions applied to the shield case, since the case-fixing electrode is disposed on the printed board for mounting the surface-mount parts, and the shield case is soldered to the case-fixing electrode.
Another aspect of the present invention provides the manufacturing method in which the solder-paste-applying method is carried out so that the solder paste is applied to the connection land electrode and the case-fixing electrode at the same time.
In the step of applying the solder paste, the solder paste is applied to the connection land electrode and the case-fixing electrode at the same time. In this case, since providing the solder with the printed board, for example, printing or applying can be finished in only one step during entire process, the number of manufacturing steps can be reduced, which leads to improvement of productivity and reduction in manufacturing cost.
Another aspect of the present invention provides the manufacturing method in which the solder-paste-applying method is carried out so that the solder paste is applied in separate stages of manufacturing to the connection land electrode and the case-fixing electrode.
In the step of applying the solder paste, the solder paste is separately applied to the connection land electrode and the case-fixing electrode. In this case, other steps of manufacturing process can be added between the step of applying the solder paste to one electrode and the step of applying the solder paste to the other electrode. This increases design freedom of manufacturing process.
According to another aspect of the manufacturing method of the present invention, the engaging portion of the shield case may be a pawl-shaped protrusion, and the case-fixing electrode may be disposed in an inner periphery of the engaging hole formed in the printed board.
In this case, the engaging portion of the shield case is a pawl-shaped protrusion, and the electrode used for affixing the case thereto is disposed in an inner periphery of the engaging hole formed in the printed board. Therefore, it is possible to reliably join and affix the shield case at the required position with high precision, so that a highly reliable electronic component can be obtained.
Further, according to another aspect of the present invention, when the engaging portion of the shield case is a pawl-shaped protrusion and the case-fixing electrode is disposed in an inner periphery of the engaging hole, the step of applying a solder paste may be carried out such that the solder paste is applied to the printed board so as to cover at least a portion of the engaging hole in the printed board, the engaging hole being used for inserting the engaging portion of the shield case therein.
In this case, in the solder-paste-applying step, the solder paste is applied to the printed board so as to cover at least a portion of the engaging hole in the printed board, the engaging hole being used for inserting the engaging portion of the shield case therein. This makes it possible to supply a sufficient amount of solder paste into the engaging hole and reliably solder the protrusion onto the case-fixing electrode, whereby a more reliable electronic component can be obtained.
In this case, it is not necessary to provide the solder into the engaging hole in such a manner that the solder is completely filled with the engaging hole. It is sufficient to provide a necessary amount of the solder to secure the engaging portion of the shield case. Thus, the amount of the solder to use can be reduced, and reduction in weight and volume of products is achieved. Since it is not required to completely fill the engaging hole with the solder, even when conditions relevant to solder-filling process change, such as the diameter of the engaging hole, the thickness of the printed board or the like, it is not necessary to adjust the amount of the solder to be filled with high precision to stabilize the supply of the solder amount. Therefore productivity is sufficiently maintained.
Since the solder is not completely filled in the engaging hole, the generation of voids in the solder to fix the engaging portion of the shield case (e.g. a pawl-shaped protrusion) and the case-fixing electrode within the engaging hole is suppressed. It is possible to easily confirm the state of affixation of the engaging portion of the shield case and the case-fixing electrode within the engaging hole. Thus the reliability is improved.
When the solder is not completely filled in the engaging hole, and a mother printed board is cut according to each region thereof where each shield case is mounted in order to divide the mother printed board into a plurality of electronic components, burrs of the solder are hard to be formed on the reverse surface of the printed board. It is because portions in which the printed board and the solder in the through hole in the same plane are cut are reduced. Solderability in mounting the electronic component is improved. Since clogging at a dicing blade caused by the solder occurs only to a small extent, the life of the dicing blade is extended. Since only a small amount of solder scraps produced by dicing are stuck onto a product, the product properties do not easily deteriorate.
Further, according to another aspect of the present invention, when the engaging portion of the shield case is a pawl-shaped protrusion and the case-fixing electrode is disposed in an inner periphery of the engaging hole, or when the solder paste is applied to the printed board so as to cover at least a portion of the engaging hole, the engaging portion of the shield case may be formed to a length that does not allow the engaging portion to protrude beyond a back surface side when the engaging portion passes into the engaging hole from a shield-case-mounting surface of the printed board.
In this case, the engaging portion of the shield case is formed to a length that does not allow it to protrude beyond the back side of the engaging hole when it passes into the engaging hole from a shield-case-mounting surface of the printed board. This makes it possible to produce an electronic component which does not have any portions protruding from the back side, which can be easily mounted, and which is suitable for high-density mounting.
According to a method of manufacturing the electronic component of the present invention, a mother printed board that is to be divided into a plurality of electronic components may be used as the printed board; in the mounting step a plurality of surface-mount parts and a plurality of shield cases may be mounted onto the mother printed board; and after the reflow soldering step, the method may further comprise the step of dividing the mother printed board into the plurality of electronic components having the surface-mount parts accommodated in the shield cases by cutting the mother printed board according to each of shield-case-mounted areas.
In this case, in the mounting step, a plurality of surface-mount parts and a plurality of shield cases are mounted onto a mother printed board, and after the reflow soldering step the mother printed board is cut according to each of shield-case-mounted areas in order to divide the mother printed board into individual electronic components. This allows many electronic components to be produced efficiently.
It is possible to apply (supply) solder paste to a mother printed board that is to be cut into a plurality of electronic components and that does not have too small a size. Therefore, it is possible to increase the precision with which the solder paste is supplied to the proper locations and the proper amount of solder paste is supplied. Consequently, efficient production of highly reliable electronic components can be achieved without being restricted by the sizes of individual products. As a result, it is possible to, for example, reduce facility size and working space.
An opening may be formed in at least a portion of the shield case or at least a portion of each shield case, and after soldering the surface-mount part or each surface-mount part and the shield case or each shield case onto the printed board, or after cutting the printed board in the dividing step, an inside of the shield case or each shield case may be cleaned.
In this case, an opening is formed in the shield case or each shield case, and after soldering the surface-mount part or each surface-mount part and the shield case or each shield case onto the printed board, or after cutting the printed board in the dividing step, the inside of the shield case or each shield case is cleaned. Therefore, for example, flux or solder balls produced by the soldering or scraps produced when the board is cut can be removed, thereby reliably preventing quality deterioration.
The location where an opening of the shield case or each shield case is formed is not particularly limited, so that it can be formed in any location. In general, when the shield case or each shield case is a square-shaped case as viewed in a plane, it is preferable that an opening be formed in a pair of opposing side surfaces or in each of four side surfaces. This allows the inside of a shield case to be efficiently cleaned.
According to another aspect of the present invention, there is provided an electronic component produced by the above-described methods, wherein the electronic component has a structure in which the surface-mounted part is soldered onto the connection land electrode on the printed board, and in which the shield case for accommodating the surface-mounted part is soldered onto the case-fixing electrode on the printed board, the shield case having an opening for cleaning the inside of the shield case.
Since the electronic component has a shield case with an opening for cleaning the inside of the shield case in addition, the electronic component can be efficiently produced by the above-described methods. Therefore, stains, such as flux or solder balls produced by the soldering or scraps produced when cutting the board can be cleaned off and removed, thereby maintaining a predetermined quality, so that reliability is enhanced.